So, since I've nuked my storage and reinstalled everything from scratch, I've been having issues with graphical performance.
My PC specs:
Dell Inspiron 5437-A20
Intel Core i7-4500U
8GB DDR3 RAM
Intel HD Graphics 4400 + NVIDIA Geforce GT 750M (running under Bumblebee)
250GB SSD (Samsung EVO 850) + 1TB HDD
Logs from lspci, lshw, dmesg and configuration files are here: http://pastebin.com/nFkmhDx5
I used to use Xubuntu 14.04, without any issues. Everything ran pretty. I then migrated to the latest Debian with Gnome 3 (since I had issues related to executing dangerous commands without care, and I was already planning to try Debian), and everything ran pretty sluggish - even moving a window around would lag the hell out of my PC. I tried various other desktop environments - KDE Plasma, Cinnamon, Unity... every compositing DE I tried would just lag horribly.
I then tried nuking it all over and switching to Linux Mint 18, with Cinnamon. It ran as slow as Debian. I eventually settled with MATE + Openbox, a non-compositing environment which works well enough for most tasks and looks well enough, but certain applications still lag a bit.
I'm also using Bumblebee for NVIDIA Optimus support. And the NVIDIA card runs really well on games - everything runs smooth, except for the display updates on the Intel display which cause lag and some tearing. And if I try running anything that's hardware accelerated on the Intel GPU - WebGL, HTML5 Canvas games, Minecraft... it lags horribly. The only things that work smoothly are SDL-based applications.
And yes, I've tried it without Bumblebee - same result, it lags like hell... and I'm not willing to use the NVIDIA card all the time because it causes micro-stuttering when used as the default card. and drains the battery like crazy.
I've tried everything - updating the Intel Graphics driver, tweaking configurations around - I even built the latest stable version (4.4.20) of the Linux Kernel from kernel.org. Nothing seems to do any effect.
I'm getting crazy over this issue. 60FPS videos micro-stutter unless they're played in a small window, scrolling web pages stutter, and I can't even play goddamn .io games without lag.
I'd like to know what can I do to try and fix this problem.